diff --git a/src/bus.rs b/src/bus.rs
index b243803..33b8206 100644
--- a/src/bus.rs
+++ b/src/bus.rs
@@ -88,7 +88,7 @@ impl Bus {
             },
             0x8000..=0x9FFF => {
                 // 8KB Video RAM
-                self.ppu.vram[(addr - 0x8000) as usize]
+                self.ppu.read_byte(addr)
             }
             0xA000..=0xBFFF => match self.cartridge.as_ref() {
                 // 8KB External RAM
@@ -97,11 +97,11 @@ impl Bus {
             },
             0xC000..=0xCFFF => {
                 // 4KB Work RAM Bank 0
-                self.wram.read_byte((addr - 0xC000) as usize)
+                self.wram.read_byte(addr)
             }
             0xD000..=0xDFFF => {
                 // 4KB Work RAM Bank 1 -> N
-                self.vwram.read_byte((addr - 0xD000) as usize)
+                self.vwram.read_byte(addr)
             }
             0xE000..=0xFDFF => {
                 // Mirror of 0xC000 to 0xDDFF
@@ -141,7 +141,7 @@ impl Bus {
             }
             0xFF80..=0xFFFE => {
                 // High RAM
-                self.hram.read_byte((addr - 0xFF80) as usize)
+                self.hram.read_byte(addr)
             }
             0xFFFF => {
                 // Interrupts Enable Register
@@ -168,7 +168,7 @@ impl Bus {
             }
             0x8000..=0x9FFF => {
                 // 8KB Video RAM
-                self.ppu.vram[(addr - 0x8000) as usize] = byte;
+                self.ppu.write_byte(addr, byte);
             }
             0xA000..=0xBFFF => {
                 // 8KB External RAM
@@ -179,11 +179,11 @@ impl Bus {
             }
             0xC000..=0xCFFF => {
                 // 4KB Work RAM Bank 0
-                self.wram.write_byte((addr - 0xC000) as usize, byte);
+                self.wram.write_byte(addr, byte);
             }
             0xD000..=0xDFFF => {
                 // 4KB Work RAM Bank 1 -> N
-                self.vwram.write_byte((addr - 0xD000) as usize, byte);
+                self.vwram.write_byte(addr, byte);
             }
             0xE000..=0xFDFF => {
                 // Mirror of 0xC000 to 0xDDFF
@@ -233,7 +233,7 @@ impl Bus {
             }
             0xFF80..=0xFFFE => {
                 // High RAM
-                self.hram.write_byte((addr - 0xFF80) as usize, byte);
+                self.hram.write_byte(addr, byte);
             }
             0xFFFF => {
                 // Interrupts Enable Register
diff --git a/src/high_ram.rs b/src/high_ram.rs
index 195e5b6..38b068f 100644
--- a/src/high_ram.rs
+++ b/src/high_ram.rs
@@ -12,11 +12,11 @@ impl Default for HighRam {
 }
 
 impl HighRam {
-    pub fn write_byte(&mut self, index: usize, byte: u8) {
-        self.buf[index] = byte;
+    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+        self.buf[addr as usize - 0xFF80] = byte;
     }
 
-    pub fn read_byte(&self, index: usize) -> u8 {
-        self.buf[index]
+    pub fn read_byte(&self, addr: u16) -> u8 {
+        self.buf[addr as usize - 0xFF80]
     }
 }
diff --git a/src/ppu.rs b/src/ppu.rs
index ac34d29..28ff611 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -15,6 +15,16 @@ pub struct Ppu {
     cycles: Cycles,
 }
 
+impl Ppu {
+    pub fn read_byte(&self, addr: u16) -> u8 {
+        unimplemented!()
+    }
+
+    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+        unimplemented!()
+    }
+}
+
 impl Ppu {
     pub fn step(&mut self, cycles: Cycles) {
         self.cycles += cycles;
diff --git a/src/work_ram.rs b/src/work_ram.rs
index 0e987de..aa1f900 100644
--- a/src/work_ram.rs
+++ b/src/work_ram.rs
@@ -4,12 +4,12 @@ pub struct WorkRam {
 }
 
 impl WorkRam {
-    pub fn write_byte(&mut self, index: usize, byte: u8) {
-        self.bank[index] = byte;
+    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+        self.bank[addr as usize - 0xC000] = byte;
     }
 
-    pub fn read_byte(&self, index: usize) -> u8 {
-        self.bank[index]
+    pub fn read_byte(&self, addr: u16) -> u8 {
+        self.bank[addr as usize - 0xC000]
     }
 }
 
@@ -56,11 +56,11 @@ impl VariableWorkRam {
         self.current
     }
 
-    pub fn write_byte(&mut self, index: usize, byte: u8) {
-        self.bank_n[self.current as usize][index] = byte;
+    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+        self.bank_n[self.current as usize][addr as usize - 0xD000] = byte;
     }
 
-    pub fn read_byte(&self, index: usize) -> u8 {
-        self.bank_n[self.current as usize][index]
+    pub fn read_byte(&self, addr: u16) -> u8 {
+        self.bank_n[self.current as usize][addr as usize - 0xD000]
     }
 }